This invention relates to the repair of stone chips and related cracks in automotive windshields. More particularly this invention relates to a repair resin head which consecutively injects resins having different viscosities.
Automotive windshields frequently chip when they deflect small stones thrown off or up by moving vehicles immediately ahead on a roadway. Road vibration and temperature changes cause cracks first to diverge from these chips, and then spread across the windshield. After a crack has grown excessively, the windshield must be replaced.
Because the substantial replacement and labor cost of installing a new windshield can be saved by repairing the stone chip and small crack extending therefrom, many tools have been devised to inject resin into a stone chip and the crack extending therefrom. Most all of these tools have a resin injection head on one end portion, a suction hold down cup on a central portion, and a head pressure adjusting screw on the opposite end portion; so the tool, spaced from the windshield by the suction cup, and the injection head seated above the crack or chip, may be dragged along the crack injecting resin therein.
Many repair procedures comprise injecting resins of different viscosities into a chip and crack. It is difficult to fill a deep and wide chip with a relatively thin resin having a low viscosity. The resin runs out of the chip. Similarly it is difficult to penetrate a deep tight crack with a relatively thick resin having a high viscosity. Intermediate open portions of the crack can be filled first with thick resin and then finished with thin resin to ensure optimal bonding between the thick resin and the top edges of the crack. Secondary use of a thin resin also fills in voids and bubble openings in the thicker resin resulting in a stronger bond and smoother finish. Alternatively, bonding may be improved when the crack is first wetted with thinner resin, and then filled with thicker resin.
In all of these procedures which utilize resins of different viscosities it is necessary to set up, drag along, and remove the repair tool from the windshield more than once. In addition to being time consuming, it is particularly disadvantageous to flex the windshield along the crack any more than necessary because this flexing frequently causes cracks to grow.
It is an object of this invention to disclose a multi-injection head which facilitates injection of resins having differing viscosities into a chip and related crack. It is an object of this invention to disclose a multi-injection head which allows a chip and extending crack to be repaired with a single set up and pass of a repair tool thereby minimizing windshield flexing. It is yet a further object of this invention to disclose a multi-injection head which can be utilized in almost any existing windshield repair tool to better repair chips and related cracks. Cracks typically have variable width and stress therealong. For example, a crack may be closed, partially open, then open and closed again where it turns. The multi-injection head accommodates varying widths in cracks. The viscosity of the resin can be varied as the head is dragged along a crack having a variable width. Additionally, the head can be twisted to vary the order of injection of the thicker and thinner resins, as well as to more closely follow a turning crack.
One aspect of this invention provides for a multiple injection head for injection of resins having different viscosities into a chip/crack on an automotive windshield. The multiple injection head comprises: a) a plunger housing having a top side portion, a bottom side portion, and two cylindrical openings each extending from the top side portion through to the bottom side portion thereof, said openings each having an upper internally threaded portion and a lower chamber portion; and, b) two generally cylindrical plungers each having an upper portion adapted to be hand turned, an intermediate portion matingly threaded with respect to the housing, and a lower portion. When the resins having different viscosities respectively fill the chamber portions, the plungers can be turned into the threaded portions of the openings controllably and selectively forcing the resins through the openings out of the bottom side portion of the housing into a chip/crack therebelow on the windshield. As the head is dragged along the chip/crack first one viscosity resin is injected, and then the other different viscosity resin is immediately injected into the crack/chip producing an unusually smooth and strongly bonded crack in a single pass.
Within this specification chip/crack is defined to mean a chip and a related crack extending from the chip, or a crack alone, or a chip alone.
In a preferred aspect of the multi-injection head is adapted for use with a repair tool having an internally threaded head opening therein. Then the housing is generally cylindrical and a lower portion of the housing has a mating external thread therearound so that the head can screw into the repair tool; and subsequently, the head can be rotated for height adjustment, and be minimally rotated in the tool to facilitate following a curved crack in the windshield.
Various other objects, advantages and features of this invention will become apparent to those skilled in the art from the following description in conjunction with the accompanying drawings.